The magic number of 123 extents per volume is because the primary space in the 
DEFINE can actually take up to 5 extents to satisfy the request.  Adding the 4 
'secondary primary' extents to the 123 total extents totals the 127.

Rex

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf 
Of John Gilmore
Sent: Thursday, November 21, 2013 11:12 AM
To: [email protected]
Subject: Re: Extents limit for HFS

Why the magic number of 123 extents per volume?  127 is more
plausible.   What else is going on here?

On 11/21/13, John Eells <[email protected]> wrote:
>
> z/OS DFSMS Using Data Sets, topic 3.9.2.1, "Creating HFS Data Sets":
>
> ...
>
> These data sets can expand to as many as 255 extents of DASD space on
> multiple volumes (59 volumes maximum with 123 extents per volume).
>

John Gilmore, Ashland, MA 01721 - USA

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